During the construction or maintenance of elevated structures such as buildings, bridges, walkways, towers, monuments, and the like, temporary scaffold systems are often erected around the perimeter of the structure to support the workers engaged in construction or maintenance activities. These scaffold systems are also typically configured and/or covered to control or inhibit the falling of debris onto other workers or passersby, for example, being enclosed within a protective or containment barrier, generally comprised of flexible plastic sheeting that surrounds both the structure and the scaffold system. Such barriers generally are required to contain or prevent any harmful chemicals or nuisance products of construction from escaping into the surrounding environment.
As illustrated in FIG. 1A, one common application for a scaffold system 20 installed around an elevated structure 10 and which requires an outer containment barrier 50 is the periodic sand blasting and re-painting of structures, such as a water tower 12 for maintenance purposes. Water towers and other, similar structures generally have cylindrical or substantially non-planar shapes, and thus the scaffold system typically must be installed in a curved arrangement to provide walkways that substantially conform to the rounded perimeter of the tower 12. The curved scaffold system 20 will generally comprise a plurality of end frames 32 that are stacked top-to-bottom, and will be connected laterally to one another with cross-bracing (not shown) with walk-through openings defined therebetween, to form the scaffold framework 24. Planking 40, typically comprising sets of side-by-side planks 42, is placed on cross bars 36 extending along the tops of the end frames 32, spanning the spaces between the end frames, often in alternating overlapping fashion between segments of the scaffold framework 24, so that workers can move along the walkways formed thereby to conduct their activities. Federal Safety Regulations require the planking be “complete” between the outer posts of the end frames, with no gaps therebetween. The outer containment barrier 50 formed from flexible sheeting 52 is then attached or shrink-wrapped around the outer perimeter of the scaffold framework 24 to seal both the elevated structure 10 and the scaffold framework, including the planking 40, within the volume defined by the outer sidewall of the water tower 12 and the inside surface of the containment barrier 50.
However, even as the arrangement of end frame columns 30 within the scaffold system 20 is curved to follow the contours of the water tower 12, the rectangular shape of the planks 42 of the planking 40 structure, and the requirement that all of the planks 42 be fully supported by cross bars 36 at both ends, does not lend itself to a smooth cylindrical contour. As a result, where curved scaffold systems 20 are used, this often results in the corners 44 of the outermost planks projecting outwardly beyond the outermost uprights 34 of the end frames 32, as shown in FIG. 1B. Since the flexible sheeting 52 must be pulled tight against the scaffold system structure to ensure proper containment, the corners 44 can create stress points 56 at the joints about the curved structure. Over time, wind and other elemental forces and localized motions of the scaffold system 20 caused by the workers moving therealong, can initiate tearing in the sheeting 52 at the stress points 56, creating holes in the containment barrier 50 that, if left uncorrected would allow chemicals or nuisance products of construction to escape into the surrounding environment. Such breaches of containment are impermissible per applicable environmental and safety regulations, the damage to the sheeting 52, and thus may require premature replacement of one or more sections of the containment barrier 50.
Consequently, a need exists for a scaffold system that provides for an efficient and low cost structure that meets regulatory requirements for safety and support when erected next to non-planar elevated structures while maintaining the integrity of the containment barrier. It is toward such a scaffold system that the present disclosure is directed.